Projects this Summer
Get flash to fully experience Pearltrees
A stepper motor is a motor controlled by a series of electromagnetic coils. The center shaft has a series of magnets mounted on it, and the coils surrounding the shaft are alternately given current or not, creating magnetic fields which repulse or attract the magnets on the shaft, causing the motor to rotate. This design allows for very precise control of the motor: by proper pulsing, it can be turned in very accurate steps of set degree increments (for example, two-degree increments, half-degree increments, etc.). They are used in printers, disk drives, and other devices where precise positioning of the motor is necessary. There are two basic types of stepper motors, unipolar steppers and bipolar steppers.
As seems to be the case with many of my projects , for this one, I acquired the parts first, and then designed a project to fit the parts I had. Here is the back story of how I got the parts, and what drove me to use them to build the vehicular monstrosity this post is about. But first, a brief overview of the scooter's specs: Motors: 3x CIM motors Batteries: 8x Turnigy 5000 mAh 4s LiPo packs , 16s2p configuration (59.2V, 10 Ah) Controller: Kelly KDS72200E , 72V, 120 A continuous, 200A peak Wheels: 12.5" with knobby pneumatic tires Deck: Hand laminated carbon fiber with polycarbonate top Frame: Royce Union Transit kick scooter, with about 200% more aluminum added Brake: Pedal actuated rear disk (sprocket) brake Videos are at the bottom of the post. At the beginning of this past school year, my school's robotics team decided to finally dismantle some old FRC robots that had been collecting dust for six or seven years.
If you are familiar with LED flashers using transistor, you may know the basic one uses two transistor, one capacitor and three resistors. There is other kind of oscillator called "flip-flop". As I'm starting to develop some basic circuits, I need a simple LED flasher that can be used in many other applications. After some hours thinking how to create a new simple LED flasher with the minimum components, I decided to use a simple RC. Here is the schematic of my two-transistor LED flasher:
I made a simple heartbeat sensor using an Arduino which sends OSC signals at each heartbeat over a network. I'm using the heartbeat sensor as an awesome prop in my show . . Recotana also wrote the which enabled this project. // cpm_heartbeatEthernet // Version 1.0 October 2009. // Copyright Charles Martin (http://www.charlesmartin.com.au). // Uses recotana's OSCClass (http://www.recotana.com) // Detect heartbeat using a light reading through skin // On each beat, send an OSC message of the instantaneous // heartrate.
Principles of Pulse Oximetry Technology: The principle of pulse oximetry is based on the red and infrared light absorption characteristics of oxygenated and deoxygenated hemoglobin. Oxygenated hemoglobin absorbs more infrared light and allows more red light to pass through. Deoxygenated (or reduced) hemoglobin absorbs more red light and allows more infrared light to pass through. Red light is in the 600-750 nm wavelength light band.
Principles: Sense heart rate by using a pair of infrared emitter and reciever, next to each other on top the measuring site on top of the finger. The light bounces from the emitter to the detector across the site. with each heart beat the heart contracts and there is a surge of arterial blood, which momentarily increases arterial blood volume across the measuring site. This results in more light absorption during the surge. if light signals received at the photodetector are looked at 'as a waveform', there should be peaks with each heartbeat and troughs between heartbeats.
This video shows how to create an infrared heart sensor using an Arduino controller, a couple of resistors, and an infrared light emitter and detector. This device will be used on the subject's finger, detecting the amount of blood which is flowing through the subject's finger. The amount of oxygenation of the blood is shown in the finger, which will cause the infrared light to reflect off the skin and to the transmitter which is close by. The fluctuations of oxygenation are picked up by the sensor, which you should wire to the Arduino.
Multiplexed displays are electronic displays where the entire display is not driven at one time. Instead, sub-units of the display (typically, rows or columns for a dot matrix display or individual characters for a character orientated display, occasionally individual display elements) are multiplexed, that is, driven one at a time, but the electronics and the persistence of vision combine to make the viewer believe the entire display is continuously active. 10x8 LED dot matrix display: Below figure illustrates the construction of a 10x8 LED dot matrix display.
Although it is possible (and tempting) to use LEDs of different colors, it is recommended you stay with ones with similar voltages: reds, ambers, and greens are in the 2v range, while blue, purple and whites are 3v or more. This avoids the problem with grossly varying brightnesses. Begin with a 2" x 3" (5cm x 7.5cm) piece of perforated circuit board (perfboard) and arrange the LEDs as shown. Align the SHORTER (-) leads towards the top of the board, which I had marked with an arrow.
Time lapse, also known as intervalometry (as in measuring intervals between photographs), is a method of taking pictures slowly over time and then compiling them into a video of compressed time. I've always been fascinated with time lapse videos. I remember when I was very young, seeing a time lapse video of a vine growing and creeping around at night. I was amazed! A good time lapse video can change your whole perspective and understanding of seemingly uninteresting everyday things. I always assumed that making these videos would require specialized equipment that would be out of my price range.
' Once it's tested and working, you'll find that it's a real conversation piece at your next party or dance. You can slip it inside a shirt pocket with the perfboard on the outside. The mic will pick up the sound from around you and the LEDs will 'perform' to it. A final touch - cut short pieces of a clear or translucent drinking straw to fit over the tops of the LEDs. This will spread the light to give you the 'bar of light' effect.